Photographic emulsion



Patented Feb. 11, 1941 UNITED STATES 2,231,653 rno'roGnAPmo EMULsIoN Leslie G. S. Brooker and Lloyd A. Smith, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application December 16, 1937, Serial No. 180,214

14 Claims.

This invention relates to new dyes and to photographic emulsions containing the same.

This application is a'continuation-in-part' of our co-pending application Serial No. 133,524,

med March 29, 1937.

A number of cyanine dyes are known and some of these have been found to sensitize photographic emulsions in a number of different useful manners. We have now found that cyanine dyes of the sensitizmg types, in which at least one of the alkyl groups on the cyaninev nitrogen atoms is an oxygen-containing alkyl group which is devoid of aryl group substituents or a cyanol er1-containing alkyl group which is devoid of aryl group` substituents or a halogen-containing alkyl group which is devoid of aryl group substit-l uents are very useful sensitizers from various standpoints. Our new sensitizers are particularly useful in sensitizing photographic emulsions to light of longer wavelengths, i. e. to light of the red, far-red and infra-red regions of the spectrum. y

Accordingly, it is among the objects of our invention to provide new photographic emulsions photographic emulsions sensitized to the red, far. red and infra-red with new cyanine dyes. A further object is to provide a process for sensitizing photographic emulsions, `particularly to the red, far-red and infra-red.v A still further object is to provide a photographic element comprising an emulsion sensitized with our new dyes. A still further object is to provide new cyanine o dyes and intermediates therefor. A still further object is to provide a process for preparing our new cyanine dyes and the intermediates therefor. The mode of accomplishing these objects and other more specific objects will become apparent Aupon a complete perusal of the following specication and claims.

The oxygen-containing alkyl groups contemplated in our invention include, for example, hydroxyalkyl, alkoxyalkyl, acyloxyalkyl, Carbalkoxyalkyl, acylalkyl, hydroxyalkoxyalkyl and alkoxy-alkoxyalkyl groups which are devoid of aryl substituents. The cyanogen-containing alkyl groups contemplated in our invention include, for example, cyanalkyl groups which are devoid of groups contemplated in our invention include, for example, chloralkyl, bromalkyl, iodalkyl and iluoralkyl groups which are devoid of aryl-substituents. The reasons for the specific eects of the oxygen, cyanogen or halogen in the alkyl groups are Anot at present known.

Our new dyes can be prepared from cyclammonium quaternaryv salts which salts can bepro-` 60 sensitized with new cyanine dyes, particularlyaryl substituents. The halogen-containing alkyl pared ashereinafter set forth. lCyclammoniurn 1 alkoxyalkyl quatemary salts can be prepared, for example, by reacting a heterocyclic nitrogen base with an alkoxyalkyl ester. We have found that the alkoxyalkyl toluenesulfonates are advantageously employed. Heat accelerates the formation of the quaternary salts. Diluents can be employed in the reaction mixture, though they are not essential. The alkoxyalkyl toluenesulfonate quaternary salts can be converted into the less soluble quaternary salts e. g. the alkoiwalkyl halides and perchlorates, by treating solutions of the toluenesulfonate quaternary salts with solutions of soluble halides or perchlorates as hereinafter set forth.

While our method of obtaining alkoxyalkyl quaternary salts is subject to variation, particularly as respects the nature and quantity of heterocycllc nitrogen base employed, the nature and quantity of alkoxyalkyl ester employed, the temperatures employed, the time of Vreaction employed, the nature and quantity of diluent employed, if any, and the method of isolation and purification of the quaternary salts and the method of converting the toluenesulfonate quaternary salts to the other quaternary salts, the following examples will serve to illustrate the mode of obtaining our new quaternary salts. These examples are not intended to limit our invention.

EXAMPLE 1.-1-methyIbeneothazoIeethoxyethiodide EXAMPLE 2,-Qunaldine--ethoxyethiodide 7.2 g. (1 mol.) of quinaldine and 12.2 g. of, ethoxyethyl-p-toluenesulfonate were heated together for about seven days at about 100 C. The crude reaction product was dissolved in methyl alcohol andthe resulting solution treated with diethylether toprecipitate the quaternary salt. 2.6 g. of the precipitated product wasdissolved in 20 cc. of methyl alcohol, and treated with 2 g. of potassium iodide dissolved in sufficient water to form a 50% (by weight) solution. The alkoinr` alkiodide was obtained -asfreiidisli crystals obtained by carefully concentrating` the' solution..

'The crystals .werenot lfurther purifled.` l

-the mixture alkaline.

7.2 (1 mol.) of lepidine and 12.2 g. (1 mol.) of -ethoxyethyl-p-toluenesulfonate were heated together for about five days at about 100 C. The crude reaction product was dissolved in about 50 cc. of water and treated with 11.5 g. of potassium iodide dissolved in suicient waterv to form an 88% (by Weight) solution in water. 'I'he alkoxyalkiodide separated from the solution. It was recrystallized from methyl alcohol and obtained as yellow crystals melting at 129 to 131 C. with decomposition.

In a manner similar to that illustrated in the above examples, 1-methylbenzoselenazole, amethylnaphthothiazoles, ,t methylnaphthoxazoles, 1methylbenzoxazoles, 4-phenyl-2-methylthiazole, 2-methyl-5,6benzoquinolines, 4-phenyl- 2-methyloxazole, 2-methylthiazoline, 1methyl mercaptobenzothiazole, 1-phenylmercaptobenzothiazole for example can be converted into alkoxyalkyl quaternary salts.

The alkoxyalkyl-p-toluenesulfonates employed in the above examples can be prepared by al method similar to that described by Fldi in Berichte der deutschen chemischen Gesellschaft, vol. 53, page 1836 (1920), for preparing esters of benzene sulfonic acid. The following example is illustrative:

EXAMPLE 4.--Ethomyethyl-p-toluenesulfonate 22.5 g. (1 mol.) of ethylene glycol monoethyl ether and 47.5 g. (1 mol.) of p-toluenesulfonyl chloride were mixed by stirring together. The mixture was chilled in an ice-salt bath. A 20% (by weight) aqueous solution of sodium hydroxide Was added to the mixture dropwise and the tem- Derature of the mixture was held below 10. C. Suicient sodium hydroxide was added to make After alkalinity was reached, the mixture was stirred for a further fifteen minutes. 48 cc. (1.12 mol.) of sodium hydroxide solution were added. 300 cc. of Water were then added to the mixture. The oily layer was taken up in benzene. The'benzene extract was dried over anhydrous potassium carbonate, the benzene distilled away and the residue distilled in vacuo. ,B-Ethoxyethyl-p-toluenesulfonate was obtained as a practically colorless liquid boiling at 157 to 158 C. at 2 mm. Instead of employing'alcohols such as -ethoxyethyl alcohol, alcohols such as diethylene glycol monomethyl ether or diethylene glycol monoethyl ether can be employed.

Cyclammonium acyloxyalkyl quaternary salts can be prepared, for example, by reacting a heterocyclic nitrogen base with an acyloxyalkyl ester. We have found that acyloxyalkyl halides, particularly bromides, are advantageously employed. Heat accelerates the formation of the quaternary salts. Diluents can be employed in the reaction mixture, though they are not essential. 'I'he acyloxyalkyl bromide quaternary salts can be converted into the less soluble quaternary salts, e. g. the acyloxyalkyl iodides or perchlorates,

by treating ysolutions of the quaternary salts with solutions of soluble halides or perchlorates as p,

hereinafter described.

While our method oi.' obtaining acyloxyalkyl quaternary salts isV subject to variation particularly as respects the nature and quantity of heterocyclicvnitrogen bases employed, the nature and quantityV of acyloxyalkyl ester employed, the

.temperatures employed, the 'time of reaction employed, the nature and quantity of diluent emv ployed, if any, and the method of isolation and `purification of the quaternary salts and thev method of converting the bromide quaternary salts into other quaternary salts, the following examples will serve to illustrate the mode of obtaining our new quaternary salts. These examples are not intended to limit our invention.

EXAMPLE 5.-1 methylbeneothzazole acetoyethiodide 14.9 g. (1 mol.) of 1methylbenzothiazole and 16.7 g. (1 mol.) of -bromethyl acetate were heated together at about 100 C. for about one week. A The crude reaction product was dissolved in about 15 cc. of water and the resulting solution treated with 14 g. (1 mol. plus 50% excess) of potassium iodide dissolved in a small amount of water. The acyloxyalkyl iodide separated out. It was twice recrystallized from methyl alcohol decolorizing the alcoholic solution with activated charcoal. It was obtained as nearly colorless crystals melting at 200 to 201 C.

EXAMPLE 6.-Lepidz'ne-,8-acetoxyethiodide 28.6 g. (1 mol.) of lepidine and 33.4 g. (1 mol.) oi' -bromethyl acetate were heated at about 100 C. for about four hours. The crude reaction product was dissolved in about 40 oc. of hot water and the resulting solution treated with 39 g. (1

mol. plus 50% excess) of potassium iodide dissolved in a small amount of water. The acyloxyalkyl iodide separated. It was twice recrystallized from methyl alcohol and obtained as yellow crystals melting at 177 to 178 C.

In a manner similar to that illustrated in the above two examples, acyloxyalkyl quaternary `salts of quinaldines, aand 'y-picolines, l-methylbenzoxazole, 1methylbenzoselenazole, ,l-methylnaphthothiazoles, a methylnaphthoxazoles, 2 methyl -4- phenylthiazoles, 2- methyl -4- phenylselenazole, 2-methyl--phenyloxazole, 2-halogenoquinolines, 4-chloro-l-methylbenzothiazole, 2,4- dimethylthiazole, 1 methylmercaptobenzothiazole, l-methylmercaptobenzoxazole and 1-phenylmercaptobenzothiazole, for example, can be prepared.

Cyclammonium acylalkyl quaternary salts can beprepared, for example, by reacting a heterocyclic nitrogen base with a halogenoketone. We have found that chloroketones are advantageously employed. Heat accelerates the formation of the quaternary salts. Diluents can be employed in the reaction mixture, though they are ordinarily not to be preferred. The acylalkyl chlorides can be converted into the less soluble quaternary salts, e. g. the acylalkyl iodides or perchlorates, as hereinafter set forth.

While our method of obtaining acylalkyl quaternary salts is subject to variation, particularly as respects the nature and quantity of heterocyclic nitrogen base employed, the nature and to illustrate the mode of obtaining our new quaternary salts. These examples are notintended to limit our invention.

Examen: 7,-1-methylbenzothzazole acetony iodide 14.9 g. (ly mol.) of 1-methylbenzothiazole and EXAMPLE 8.-Lepdine acet'onyl iodide 7.2 g, (1 mol.) of lepidine and 4.6 g. (lmol.) of chloracetone were heated on the steam bath at about 100 C. for about five hours. mixture set to a solid dark mass. The mass was dissolved in about 30 cc. of methyl alcohol and converted directly to the iodide by treating the methyl alcoholic solution with a concentra-ted aqueous solution containing 9 g. of potassium iodide. The acylalkyl iodide was obtained as yellowish crystals. 'I'he yellowish crystals were twice recrystallized fromv methyl alcohol (decolorizlng the methyl alcoholic solution with activated charcoal) and obtained as yellowish crystals melting at 218 to 219 C. with decomposition.

In a manner similar to that illustrated in the above two examples acylalkyl quaternary salts of quinaldines, uand 'y-picolines, 1methylbenzoxa lzole, l-methylbenzoseleniazole, a methyl naphthoxazoles, a-methylnaphthothiazoles, 2-methyl- 4phenylthiazole, 2-methyl 4 phenylselenazole, Z-methyl-4-phenyloxazole, 2-halogenoquinolines, 4-chloro-l-methylbenzothiazole, 2,4-dimethylthiazole, l`methylmercaptobenzothiazole and 1- phenylmercaptobenzothiazole for example can be prepared.

Cyclammonium carbalkoxyalkyl Quaternary salts can be prepared for exampleby reacting a heterocyclic nitrogen base withI an ester of a vhalogenated fatty acid. We have found that bromesters are advantageously employed. Heat accelerates the formation of the quaternary salts.

Diluents can be employed in the reaction mixture,

The carballroxy-l though they are not essential. alkyl quaternary bromides can be converted into the less soluble quaternary salts, e. g. the iodides and perchlorates, by treating solutions of the bromides with solutions of soluble iodides or perchlorates as hereinafter set forth.

While our method of obtaining carbalkoxyalkyl quaternary salts is subject to variation, particularly as respects the nature and quantity of heterocyclic nitrogen base employed, the nature and quantity of bromester employed, the temperatures employed, the time of reaction employed, the nature and quantity of diluent employed, if any, and the method of isolation and purification o! the Quaternary bromides and the method of converting the-bromides to other quatemary salts, the following examples will serve to illustrate the mode of obtaining our new quaternary salts. These examples are not intended to limit our invention.

EXAMPLE 9.'-1methyzbenzothiazoze p-carbethoyethiodde f 14.9 g. 1 mol.) of 1-methy1benzothiazo1e ethicdlde and 18.1'g. l(l mol.) foi ethyl-p-bromopropiov nate were heated vin about. 25 cc. of dry .chloro. form at` the refluxing temperaturel for about one week. Dethyl ether wasl added to the cooled re' action mixture to precipitate they quaternary bromide.v The crude Quaternary bromide was dis- The reaction vnary bromide separated out.

solved in 20 cc. oi hot water and converted to the iodide by treating the hot aqueous solution with a concentrated aqueous solution containing 17.5 g. of potassium iodide. The crude iodide was slightly `pink in color. It was twice recrystallized from methyl alcohol and obtained as nearly colorless crystals melting at 131 to 133 C. with decomposition.

ExAMPLs: 10.-1-methylbenzothiazole carbethorcymethiodide ExAMPLl-i 11.-Quinaldz'ne carbethorymethiodide 28.6 g. (1 mol.) of quinaldine and 33.4 g. (1 mol.) of ethyl bromacetate were allowed to stand together at room temperature for about 24 hours. The reaction mixture set to Ia crystalline'mass. The mass was dissolved in about 25 cc. of hot water and converted to the iodide by treating the solution with a concentrated aqueous solution containing 21 g. of potassium iodide. The quaternary iodide separated as a light red crystalline powder. It was twice recrystallized from methyl alcohol and obtained as light reddish crystals melting at 192 to 194 C. with decomposition.

EXAMPLE 12.-Lepidine carbethoymethiodide 14.9 g. (1 mol.) of lepidine and 16.7 g. (1 mol.) of ethyl bromacetate Were heated in about 25 cc. of dry chloroform for about 3 days at the refluxing temperature of the chloroform. The quater- It was ltered off and dissolved in about cc. of hot water and converted to the iodide by treating the aqueous solution with a concentrated aqueous solution containing 17 g. of potassium iodide. Thel quaternary iodide separated las yellow crystals. It was twlcerecrystallizedfrom methyl alcohol and obtained as faintly yellow crystals melting at 163 to 164 C. with decomposition` In a manner similar to that illustrated in the above four examples. carbalkoxy quaternary salts of aand y-picolinesr, lmethylbenzoxazole, 1- methylbenzoselenazole, a-methylnaphthoxazoles, a methylnaphthiazoles, 2-methyl-4-phenylthiarole, 2-methyl-4-phenylselenazole, 2-methyl-4- phenyloxazole, 2-halogenoquinolines, 4`chloro1 methylbenzlothiazole, 2,4-dimethylthiazoles, 1- methylmeroaptobenzothiazole, l-phenylmercaptobenzothiazole for example can be prepared.

bromides'can be convertedinto the less soluble quaternary salts, e. g. the iodides and perchlorates,l by ltreating solutions of the 'bromides with solutions of `soluble iodidesor perchlorates as hereinbefore set forth for carba-lkoxy quaternary salts. Q

While our method of obtaining carbalkoxy vquaternary salts is subject to variation, particularly as respects the nature and quantity of heterocyclic nitrogen base employed, the nature and quantity of bromoacid employed, the temperatures employed, the time of reaction emf ployed, the'nature and quantity of diluent employed, if any, andthe method of isolationand purification of the quaternary bromides and the method of converting the bromides to other quaternary salts, the following examples. will serve to illustrate the mode of obtaining oury new quaternary salts. The examples are not intended to limit our invention.

EXAMPLE 13.--1-methylbenzothiazole carboxymethobromide 22.4 g. (l mol.) of l-methylbenzothiazole andr EXAMPLE 14.-Lepidine carbo:rymetlvobromideA 21.5 g. (1 mol.) of lepidine'and 20.4 g. (1 m01.) of bromoacetic acid were well mixed and allowed to stand at from 20 to 25 C. for about 18 hours. The resulting solid mass was dissolved in water and the quaternary bromide precipitated by addition of acetone to the aqueous solution.` The quaternary bromide was twice recrystallized from methyl alcohol and obtained as colorless crystals melting at 159 to 161 C. with decomposition.

In a manner similar to that illustrated in the above two examples carboxyalkyl quaternary salts of aand 'y-picolines, quinaldine, l-methylbenzoxazole, l-methylbenzoselenazole, a-methylnaphthotiazoles. p. methylnaphthoxazoles, 2 methyl 4 phenylthiazole, 2 methyl-4-phenyloxazole, 2 methyl- 4 phenylselenazole, 2,4-dimethylthiazole, 2-halogenoquinolines, 4-chloro-1- methylbenzothiazole, 1 methylmercaptobenzo thiazole, and 1-phenylmercaptobenzothiazole for example can be prepared.

Cyclammonium halogenated alkyl quaternary "salts can be prepared for example by reacting a heterocyclic nitrogen base with toluenesulfonate esters of halogenated alcohols. Heat accelerates the formation of the quaternary salts. Diluents can be employed in the reaction mixture, although they are not essential. The'halogenated alkyl quaternary toluenesulfonates can be converted in less soluble quaternary salts, e. g. the bromides, iodides or perchlorates, by treating solutions of the bromides with solutions of soluble bromides, iodides or perchlorates as hereinafter set forth. A

While our method of obtaining halogenated alkyl quaternary salts isl subject to variation', particularly as respects the nature and quantity of heterocyclic nitrogen bases employed. the nature and quantity o toluenesulfonate ester employed, the ltime of reaction employed, the temperatures employed, the nature and quantity of diluent employed, if any, the method of'converting the toluenesulfonatequaternary salts to other quaternary salts and the methods of isolation and purification of the quaternary salta-the fola'aaisa I lowing examples will serve to illustrate the mode of obtaining our new quaternary salts. These examples are not intended to limit our invention.

EXAMPLE 15.--1-methylbenzothiazole -chloroethz'odide EXAMPLE 16.-Lep1'dz'ne -chloroethiodide 7.15 g. 1 m01.) of lepidine and 11.7 g. 1 m01.)

`of -chloroethyl-p-toluenesulfonate were mixed and heated together at about 100 C. for 3 days. The reaction product was dissolved in water and converted directly to the quaternary iodide by treating the aqueous solution with a concentrated aqueous solution of potassium iodide containing 12.5 g. of potassium iodide. The quaternary iodide separated. It was twice recrystallized from methyl alcohol and obtained as yellowish crystals melting at 184 to 186 C. with decomposition.

In a manner similar to that illustrated in the above two examples halvogenated alkyl quaternary salts of aand y-picolines, quinaldine, l-methylbenzoxazole, l-methylbenzoselenazole, ,lt-methylnaphthothiazoles, ,L Inethylnaphthoxazoles, 2 methy1-4-phenylthiazole, 2 -methyl 4 phenyloxazole, 2 methyl 4 phenylselenazole, 2,4-dimethylthiazole, 2-halogenoquinolines, 4chloro1 methylbenzothiazole, 1 methylmercaptobenzo thiazole, and 1-phenylmercaptobenzothiazole for example can be prepared.

-Chloroethyl-p-toluenesulfonate can be prepared according to the method of Clemo and Perkin, Journal of the Chemical Society (London) vol. 121, page 642 (1922).

Cyclammonium alkyl quaternary salts contain ing va cyanogen group on the alkyl group can be prepared for example'by reacting a heterocyclic nitrogen base'with a toluenesulfonate ester of a cyanoalcohol. Heat accelerates the formation of the quaternary salts. Diluents canbe employed in the reaction mixture, although they are not essential. 'I'he cyanoalkyl quaternary toluenesulfonates can be converted into the less soluble quaternary salts, e. g. the bromides, iodides or perchlorates, by treating solutions of the toluenesulfonates with solutions of solublev bromides.

iodides or perchlorates as hereinafter set forth.

EXAMPLE 17.-1methylbenzothiazole -cyanoethOdde 3.75 g. (1 mol.) of 1-methylbenzothiazole and 5.63 g. (1 mol) of -cyanoethyl-p-toluenesulfonate were mixed and heated together at about 100 C. for about 8 days. The reaction mass was dissolved in about 10 cc, of methyl alcohol and converted directly to the'quaternary iodide by treating the alcoholic solution with a concentrated aqueous solution of potassium iodide containing 4.15 g. of potassium iodide. The quaternary iodide separated. It was recrystallized from methyl alcohol and obtained as glittering colorless crystals having a greenish cast and melting at 251 to 253 C. with decomposition.

EXAMPLE 18.-Lpdine -Cz/anoethz'odide.

3.6 g. (1 mol.) of lepidine and 5.033A g. (1 mol.) of -cyanoethyl-p-toluenesulionate were heated together on the steam bath for about 6 days.

The reaction mass was dissolved in about 10 cc.-

of methyl alcohol and the methyl alcoholic solution treated with a concentrated aqueous solution of potassium iodide containing 5.8 g. of potassium iodide. The quaternary iodide separated. It was recrystallized from methyl alcohol,

decolorizing the solution with activated charcoal. The product consisted of colorless crystals contaminated with some yellowish crystals.

In a manner similar to that illustrated in the above two examples cyanoalkyl quaternary salts of aand fy-picolines, quinaldine, l-methylbenzoxazole, 1methylbenzoselenazole, ,LL-methylnaphtothiazoles, ,iL-methylnaphthoxazoles, 2-

oxazole, 2-methyl-4phenylselenazole, 2,4-dirrethylthiazole, 2-halogenoquinollnes, 4-chloromethylbenzothiazole, l-methylmercaptobenzoi thiazole and 1phenylmercaptobenzothlazole for .0 example can be prepared.

n -cyanoethyl toluenesulfonates can be prepared as described by Clemo and Walton in the Journal of the Chemical Society (1928), page 723. 42in the foregoing seventeen examples of the preparation of quaternary salts, l-methylbenzothiazole, quinaldine and lepidine have been used as illustrations because many of the most useful sensitizing cyanine dyes contain such nuclei. In these three heterocyclic'nitrogen bases as well as in the other heterocyclic nitrogen bases, par-v ticularly those containing a benzene nucleus, various groups can be substituted, particularly in the benzene nuclei, 'for example groups such as dialkylamino, alkyl, alkoxy, halogen and acylamino.

Having set forth the manner of obtaining the.

intermediate necessary to the preparation of our new dyes, a-number of examples of the preparation of various cyanine dyes of the sensitizing types from such intermediates are hereinafter set forth.v

Our new intermediates can be employed in preparing simple cyanine dyes. i. e. cyanine dyes containing a single methenyl group between two heterocyclic nuclei, such as simple thiacyanines, simple oxacyanines, simple 4.4'cyanines, simple selenacyanines, simple oxathiacyanines, simple 2,2pyridocyanines, simple dibenzothiacyanines, 4,4'cyanines, pseudocyanines, such as thia-Z- cyanines, thiazolo-2'cyanines, oxa2cyanines, oxazolo-2cyanines, 2,2cyanines and benzothia2cyanines for example, and lsocyanineal such as thia4'cyanines, selena-4'cyanines and 2,4'cyanines for example. The following exmethyl- 4 phenylthiazole, 2-methyl-4-phenyl-- amples are illustrative of the manner of obtain. ing simple cyanine dyes from our new quaternary salts. These examples are not intended to limit our invention.

EXAMPLE 19,-2-(la-eirlwayethyn-1" eth1/anima' cyanine 1.0 g. (1 mol.) of 1methylbenzothiazole ethoxyethiodide and 1.03 g. (1 mol.) of 2iodo quinoline ethiodide were heated in about 10 cc.

of absoluteethyl alcohol containing 0.73 cc. (2.1v

0.97 g. (1 mol.) of quinaldine -ethoxyethiodide and 1.03 g. (1 mol.) of 2-iodoquino1ine ethiodide were heated in about 10 cc. of absolute ethyl a1- cohol containing 0.73 cc. (2.1 mol.) of triethylamine at the reuxing temperature for about twenty minutes. The dye separated from the chilled reaction mixture. It was recrystallized from methyl alcohol and obtained as red crystals having a bluish reex and melting at 139 to 141 C. with decomposition. The dye has the following formula:

O :H1 EXAMPLE 21.-1- (-ethoyethyl) -1 '-ethyl-ZA'- cyanine iodide 1.72 g. (1 mol.) lepidine -ethoxyethiodide and 2.06 g. (1 mol.) of 2-'iodoquinoline ethiodide were heated in about 10 cc. of absolute ethyl alcohol containing 1.46 cc. (2.1 mol.) of triethylamine at the reiluxing temperature for about4 twenty minutes. 'Ihe cool'd reaction mixture was diluted with diethyl ether to precipitate the dye. The crude dye was recrystallized from methyl alcohol and obtained as brassy green needles melting at 101 to 106 C. with decomposition. A methyl alcoholic solution of the dye was bluish red. The formula of the dye is:

EXAMPLE 22. I-caTbethOxymethyl-I '-ethylthia 2'-cyanine iodide 2.73` g. (1 rial.) of ianethyibenzothiazoie carbethoxymethiodide. and 3.1 g. (1 mol.) of 2iodo -rated from the cooled reaction mixture.

'quinoline ethiodide were heated inv about 25 cc.

of absolute ethyl alcohol containing 2.2 cc. (2.1 mol.) of `triethylamine at the refluxing tempera.- ture for about twenty minutes. The dye segg; crude dye was extracted with hot methyl alcohol. The extract yielded long orange-yellow crystals upon cooling. These long orange-yellow crystals gave a yellow methyl alcoholic solution and melted at 246 to 247 C. with decomposition. This bethoxymethylthia-2'-cyanlneiodide havingl the following formula:

/S o' s 'I'he thia2cyanine is obtained by treating the reaction mixture, after removing the separated dye, with diethyl ether. I'he dye which separated was obtained, after recrystallization from methyl alcohol, as orange crystals having a greenish reex.

The thla2'cya.nine is more advantageously obtained by heating together 3.63 g. (1 mol.) of

l-methylbenzothiazole carbethoxymethiodide and 4.1 g. (1 mol.) of 2iodoquinoline ethiodide in 20 l cc. of absolute ethyl alcohol containing 2.76 s.

(2 mol.) of potassium carbonate at the reuxing temperature for about twenty minutes. The dye separated from the chilled reaction mixture. It was recrystallized from methyl alcohol and obtained as orange crystals having -a greenish reex and melting at 209 to 210 C. with decomposition. The dye has the following formula:

No thlacyanine was formed using potassium or sodium carbonate.

cyanine iodide 1.8 g. (l mol.) of quinaldine carbethoxy methiodide and 2.06 g. (1 mol.) oi' 2iodoquinoline ethiodide were heated in about 10 cc. of ethyl y 5 alcohol containing 1.5 ce. (2.1 mol.) of methyl- 3.57 g. (1 mol.) of lepidine carbethoxymethiodide and 4.1 g. (1 mol.) of 2iodoquinoline ethiodide were heated together in about 15 cc.'ot absolute ethyl alcohol containing 2.9 cc. (2.1`mol.) of triethylamine at the reiluxing temperature for about twenty minutes. Diethyl ether was added to the cooled reaction mixture to precipitate the dye. 4'I'he crude dye was recrystallized lfrom methyl alcohol and obtained as dark crystals hav- 75 ing green and blue reflexes. 'Ihe dye Cave va bluish-red methyl alcoholic solution and melted at 215 to 216 C. with decomposition.

cyanne iodide 2.82 g. (1 mol.) of lepidine carboxymethobromide and 4.1 g. (1 mol.) of 2iodoquinoline ethiodide were heated in 25 cc. of absolute ethyl alcohol containing 2.9 cc. (2.1 mol.) of triethylamine at thereiluxing temperature for about twenty minutes. The dye was precipitated from the cooled reaction mixture by adding diethyl ether to the cooled reaction mixture. The crude dye was recrystallized from a methyl alcohol and water mixture- (equal volumes) and obtained as garnet crystals having a green reex and giving a bluish-red methyl alcohol solution. 'I'he dye melted at 208 to 210 C. with decomposition and has the following formula:

EXAMPLE 26.--1 --carbethoyethyl-I -ethylthiabethoxyethiodide and 2.74 g. (1 m-ol.) of 2iodoquinoline ethiodide were heated in about 15 cc.

' of absolute ethyl alcohol containing 2.0 cc. (2.1

mol.) of triethylamine at the reiluxing temperature for aboutthree minutes. The dye sepa-v rated i'rom the cooled reaction mixture. The dye was recrystallized from methyl alcohol and 0btained as brLownish-red crystals giving an orange solution in methyl alcohol and melting at 186 to 188 C. with decomposition. It has the following formula.:

H HI ooclHl The dye is more advantageously prepared employing an alkali metal carbonate as condensing agent instead oi' triethylamine.

Examen: 27.--1 '-caTboaz/methyl-I -ethyl-Z ,4'-

cyanine iodide ilex and giving a bluish-red solution in methyl alcohol. The dye melted at 208 -to 210 C.-wlth decomposition. It has the following formula:

' iodide 3.27 g. (1 mol.) vof lepidine acetonyl iodide and 4.1 g'. (1 mol.) ci 2-iodoquinoline ethiodide were heated together in 25 cc.of absolute ethyl alcohol containing 2.9 cc. of triethylamine at the refluxing temperature for about' twenty minutes. The

dye separated from the cooled reaction mixture upon the addition of diethyl etherthereto. 'I'he dye was recrystallized from methyl alcohol and obtained as beautiful green crystals having a bronze reflex and giving a bluish-red methyl alcohol solution. 'I'he dye melted at 233 to 235 C. with decompositio-n. It has the following formu- 3.63 g. (1 mol.) of 1methylbenzothiazole acetoxyethiodide and 4.1A g. (1 mol.) of '2-iodoquinoline ethiodide were heated together in 25 cc. of absolute ethyl alcohol containing 2.65 g. (2.5 mol.) of anhydrous sodium carbonate at the refluxing temperature for about twenty minutes.v

The dye separated from the cooled reaction mixture. After recrystallization from methylalcohol, the dye was obtained as a reddish powder which gave an orange methyl alcoholic solution. The dye melted at 268 to 269- C. with decomposition. It has the following formula:

a golden reflex and giving an orange methyl alcoholic solution. The dye melted at 263 to 265 C. with decomposition. The dye has the following formula:

g im v EXAMPLE 3l.-2- (-chloroethzrl) -1 '-ethyltha-Z'- cyanine iodide 1.7 g. (1 mol.) of 1-methyl'nenzothiazole chloroethiodide and 2.06 g. l(1. mol.) of 2-iodoquinoline ethiodide were heated together in 20 cc. absolute ethyl alcohol containing 1.5 cc. (2.1

Y mol.) oftriethylamine at the reiluxing temperawas obtained as brick colored glittering crystals which gave an orange methyl alcoholic solution.

It melted at 258 to 261 C. with decomposition.

In the above examples of the preparation of simple cyanines, ethyl alcohol has been employed exclusively as a diluent in the reaction mixture l because the reactions proceed well at the reuxing temperature of the alcohol, i. e. from 70' to C. Other diluents can be employed. e. g. methyl alcohol or n-propyl alcohol. The reactions can be carried out without a diluent, although it is diflcult to isolate the dyes under such conditions.

In the above examples of the preparation of 2'cyanine, i. e. pseudocyanine, dyes, the basic condensing agent employed in a large number of the cases has been triethylamine. Strong tertiary 'organic bases, that is, tertiary organic bases whose aqueous solutions have dissociation constants substantially greater than that of an aqueous solution of pyridine, are particularly suitable, e. g. N-methylpiperidine, triethanolamine, tributylamine, and triethylamine. Other basic condensing agents can be employed. As shown above in the examples, alkali metal carbonates are particularly efficacious.

2-cyanine,dyes can also be prepared by treating oxygen, halogenor cyanogen-containingalkyl quaternary salts of Z-phenylmercaptoquinoline with cyclammonium quaternary salts containing a reactive methyl group, such as 1-methylbenzothiazole, quinaldine, a-picoline, 2methy1 4-phenylthiazole or 2-methy1-4-phenyloxazole for example, according to the processes given in the above examples.

Simple thiacyanines can be prepared by treating oxygen, halogenor cyanogen-containingalkyl quaternary salts of l-methylmercaptobenzothiazole with 1methylbenzothiazole quaternary salts according to the process or the above examples. Simple oxaand selenacyanines can be similarly prepared.

Our new intermediates can be employed to prepare carbocyanine dyes, i. e. cyanine dyes containing a trimethenyl chain between two heterocyclic nuclei, such as 2,2carbocyanines, 2,4'- carbocyanines, 4,4carbocyanines, thia-2carbo cyanines, oxa-2carbocyanines, thiazolo-2"car bocyanines, selenazolo-2'-carbocyanines, thia-4'- carbocyanines, selena4'carbocyanines, Oxa-4- carbocyanines, thiacarbocyanines, dlbenzothia` carbocyanines, oxa-thiacarbocyanines, dibenzoxacarbocyanines, oxabenzothiacarbocyanines, benzoxathiacarbocyanines, thiazolocarbocyanines, thiathiazolocarbocyanines and the like. The following examples are illustrative of the manner of obtaining our new carbocyanine dyes from our new quaternary salts. These examples are not intended to limit our invention.

EXAMPLE 32.--2,2 di- (-carbethoryethyl) -thacarbocyanine iodide 3.77 g. (2 mol.) of 1-methylbenzothiazole carbethoxy-ethiodide and 2.5 cc. (3mal.) of ethyl orthoformate were heated together in 2 5 cc. of pyridine for about forty-five minutes atthe reuxing temperature. The dye separated from the chilled reaction mixture. The dye was recrystallized from methyl alcohol and obtained as dark crystals having a metallic reilex and giving chilling the reaction mixture.

alcoholic solution.

a bluish-'red methyl alcohohc solution. The dye melted at 207 to 208 C. with decomposition. It has the following formula:

EXAMPLE 33.-2,2di (-cyanoethyl) -thiacarbocyanine iodide 3.3 g. (2 mol.) of l-methylbenzothlazole `cyanoethiodide and 2.5 cc. (3 mol.) of ethyl orthoformate were heated together in 40 cc. of pyridine at the reuxing temperature for about forty-five minutes. The dye separated from the cooled reaction mixture. It was recrystallized from methyl alcoholand obtained as ne grayish crystals `having .a bronze reex and giving a bluish-red methyl alcoholic solution. It melted at 274 to 277 C. with decomposition.

EXAMPLE 34.-2,2'fdi (-chloroethyl) -thiaoarbO- cyanine iodide 3.4 g. (2 mol.) of 1-methylbenzothiazole chloroethiodide and 2.5 cc. (3 mol.) of ethyl orthoformate were heated together in 25 cc. 0f pyridine at the refiuxing temperature for about forty-ve minutes. The dye separated upon It was recrystal lized from methyl alcohol and obtained as dark brownish crystals which gave a bluish-red methyl The dye melted at 327 t0 329 C. with decomposition.

EXAMPLE 35.-2,2' di-(-acetozyethyl) -thiacarbocyanine iodide 3.63 g. (2 mol.) of l-methylbenzothiazole acetoxyethiodidevand 2.5 cc. (3 mol.) of ethyl orthoformate were heated together in 25 cc. of pyridine at the reiiuxing temperature for about forty-five minutes. The dye separated from the cooled reaction mixture. It was recrystallized from methyl alcohol and obtained as dark crystals having a greenish reflex and giving a bluish-red methyl alcoholic solution.v The dye. melted at 256 to 258vC. with decomposition.

and.4.95. cc. (3 mol.) fof ethyl orthoformate were heated together in cc. of vpyridine at the refiuxing temperature for about fourl hours. The dye was precipitated from the cooled reaction mixture by the addition of diethyl ether thereto.

The dye was recrystailized from methyl alcohol and obtained as green crystals having a brassy green reflex and giving a blue methyl alcoholic solution. The dye melted at 224 to 225 C.' with decomposition. It has the following formula:

minutes. The dye was precipitated from the reaction mixture by the addition of diethyl ether. thereto. The dye was recrystallized from methyl alcoholand obtained as fine green needles having a blue reflex, and giving a bluish-red methyl alcoholic solution. The dye melted at 249 C. to 250 C. with decomposition.

EXAMPLE BIL-72,2 di- (carboymethyl) -thiacarbocyanine bromide 5.76 g. (2'mol.) of l-methylbenzothiazole carboxymethobromide and 4.95 cc. (3 mol.) of ethylorthoformate were heated together in 50 cc. of pyridine at the reiluxing temperature for about forty-live minutes. cooled reaction mixture. It was suspended in 400` cc. of methyl alcohol and treated with 0.4 g. of guanidine carbonate.Y The guanidine salt was formed as a purplish 'crystalline powder giving a bluish-red methyl alcoholic solution and melting at 221 to 222 C.

EXAMPLE 40.-!,1'-dicarbethoymethyl-2,2' f carbocyanine iodide 3.57 g. (2 mol.) of quinaldine carbethoxymethiodide and 2.5 cc. of ethyl orthoformate were heated together in 25 cc of pyridine at the reuxing temperature for about three minutes. The dye was precipitated by adding diethyl ether to the cooled reaction mixture. After recrystallization from methyl alcohol, the dye was obtained as minute green needles with a metallic reex giving a blue methyl alcoholic solution. The dye melted at 240 to 241 C., with decomposition. `The dye has the following formula:

EXAMPLE 4I.-1,1'dicarbethozymethyl-Lf carbocyanine iodide l 7.14 g. (2 mol.) oi' lepidine carbethoxymethiodide and 4.95 cc. (3 mol.) of ethyl orthoformate were heated together in 25 ce. of pyridine at the EXAMPLE 37.-2,2'-diacetonyzthiacarbocyanine iodide 3.33 g. (1 mei.) of 1methylbenzothiazole acetonyl iodide and 2.5 cc. (3 mol.) of vethyl orthoformate were heated together in 25 cc. 'of pyridine at the reiiuxing temperature for about forty-tive reuxing temperature for about four hours. The dye separated from the cooled reaction mixture. Upon recrystallization from methyl alcohol, it was obtained as a greenish-bronze felted mat of crystals which gave a blue methyl alcoholic solutiQn. The dye melted at 189 t0 191 C.

The dye separated from the EXAMPLE 42.-2,2'di (p-ethozyethyl) -thiacarbocyanine iodide 2.0 g. (2 mol.) of 1methylbenzothiazole -ethoxyetho-p-toluenesulfonate and 1.25 cc. (3 mol.) of ethyl orthoformate were heated together in 10 lcc. of pyridine at the reuxing temperature for about forty-ve minutes. The dye was precipi-l tated as the dye-iodide by adding a concentrated aqueous solution of 1.0 g. of potassium iodide to the hot reaction mixture. The dye was recrystallized from methyl alcohol and obtained as greenish crystals having a bronze reflex and giving a. bluish-red methyl alcoholic solution. The dye melted at 212 to 214 C. with decomposition.

1,1' diethoxyethyl) 2,2 carbocyanine iodide was prepared in asimilar manner from 1.94 g. of quinaldine ethoxy-etho-p-toluenesul fonate and 1.25 cc. of ethyl ortho formate. After recrystallization from methyl alcohol, the dye was obtained as minute greenish needles which gave a blue methyl alcoholic solution and melted at 274 to 276 C. with decomposition.

3.43 g. (2 mol.) of lepidine -ethoxyethlodide and 2.5 cc. (3 mol.) of ethyl orthoformate were heated together in 15 cc. o'f acetic anhydride containing 0.45 g. (1.05 mol.) of anhydrous sodium acetate at the refluxing temperature for about one-half hour. The dye separated from the reaction mixture upon chilling. After recrystallization from methyl alcohol, it was obtained as beautiful bronze crystals which gave a green methyl alcoholic solution. The dye melted at 227 to 230 C. with decomposition. The dye has the following formula:

orthoformate, other esters of orthoformic acid can be used. Likewise, ethyl orthoacetate, ethyl orthopropionate and ethyl orthobenzoate can be employed in the above examples instead of ethyl orthoformate. cyanine dyes containing a substituent, such as 'methyl, ethyl or phenyl, at the central carbon atom of the trimethenyl chain can be prepared.

Example 43 shows the preparation of a neocyanine. Similarly other neocyanines can be prepared.

Unsymmetrical carbocyanine dyes containing oxygenated, halogenated or cyanogenated alkyl groups can be prepared by rst condensing a cyclammonium oxygenated, halogenated or cyanogenated alkyl quaternary salt containing a reactive methyl group in the alpha or gamma position, i. e. one of the so-called reactive positions, advantageously a quaternary iodide, with diphenyl-formamidine, advantageously in the presence of an organic acid anhydride, such as acetic anhydride. The resulting condensation product can then be condensed with a diierent cyclammonium oxygenated, halogenated or cyanogenated alkyl quaternary salt containing a reactive methyl group, again advantageously a quaternary iodide, in the presence of a basic condenslng agent, advantageously a. strong organic base, such as triethylamine or piperidine for example. In such a manner 2,2-rdi(,aethoxyethyl) -oxathiacarbocyanine iodide can be prepared for example.

Unsymmetrical carbocyanine dyes containing at least one oxygenated, halogenated or cyanogenated alkyl group on the cyanine nitrogen atoms and having an alkyl group, particularly one of the ordinary alkyl groups, such as methyl or ethyl, on the central carbon atom oi the triasboth a basic condensing agent and as a. diluent. Pyridine is a particularly efilcacious condensing agent. Other diluents can be added to the reaction mixture. The reactions are advantageously carried out at about the reiluxing temperature of pyridine. In a manner similar to that illustrated in the above examples, dibenzothiacarbocyanines, oxacarbocyanines, selenacarbocyanines, thiazolo-carbocyanines and thiazolinocarbocyanines containing oxygen-containingalkyl, halogen-containing-alkyl orcyanogen-containing-alkyl groups can be prepared. In the above examples, instead of employing ethyl methenyl chain can be prepared as illustrated for the dye having the following formula:

To prepare this dye, 2-methyl--naphthothiazole -ethoxyethiodlde is reacted with acetyl chloride in the presence of pyridine to give 2-acetylmethy- Using these latter esters, carbo.

same or a diderent cyclammonium quaternary salt, advantageously a quaternary iodide, containing a reactive methyl group, in the presence of a basiccondensing agent, advantageously, a strong organic base, such as triethylamine. In such a manner 2,2di(ethoxyethy1)-thiadicarbocyanine can be prepared.

Tricarbocyanine dyes can\be prepared from our new cyclammonium Quaternary salts containing a reactive methyl group as illustrated in the following examples. These examples are not intended to limit our invention.

EXAMPLE 44.-2,2di (-acetomyethyl) -thz'atricarbocyanine iodide 3.36 g. (2 mol.) of l-methylbenzothiazole acetoxyethlodide and 1.43 g. v(1 mol.) of glutaconic aldehyde dianilide hydrochloride were dispersed in cc. of absolute ethyl alcohol. To the dispersion was added 1.0 cc. (2 mol.) of piperidine and the whole was allowed to stand in an icebox for twenty-four hours. The dye separated from the reaction mixture. It was recrystallized from methyl alcohol and obtained as beautiful glittering emerald green crystals which gave a blue methyl alcoholic solution and melted at 203 to 205 C. with decomposition. The dye has the following formula:

carbocyanine iodide 3.5 g. (2 mol.) of l-methylbenzothiazole ethoxyethiodide and 1.43 g. (1 mol.) of glutaconic aldehyde dianilide hydrochloride werel dispersed in absolute ethyl alcohol containing 1.0 cc. (2 mol.) of piperidine. The mixture was allowed to stand at about 10 C. for about eighteen hours. The dye which separated was recrystallized from methyl alcohol. lIt was obtained as minute needles having a greenish-bronze reilex ,and giving a blue methyl alcoholic solution. The dye melted at 188 to 190 C. with decomposition.

- anine iodide was prepared in a similarmanner lns from l-methylbenzothia'zole p-carbethoxyethiodide. The -carbethoxyethyl dye was obtained as beautiful green crystals which gave a blue methyl alcoholic solution and melted at 142 to 145 C. with decomposition.

In a manner similar to that illustrated intheabove two examples, 2,2-, selena-, dibenzothia, thiazolino, 4,4- and thiazolotricarbocyanine dyes can be prepared. Instead of piperidine in the above two. examples, other strong organic bases can be employed for example triethylamine, tributylamine or diethylamine.

Our new cyclammonium .quaternary salts can be employed to prepare tetraand pentacarbocyanine dyes. Our new cyclammonium Quaternary salts containing a reactive methyl group, such as 1methylbenzothiazole -ethoxyethiodide or 2- methylnaphthothiazole -ethoxyetho-p-toluenesulfonate for example, can be condensed with,4 acyloxyA35-heptadiene1,7-dial ditetrahydroquinolide perchlorate or 4-acyloxy-A3'57-monotriene-1,9dial ditetrahydroquinolide perchlorate, in the presence of pyridine or piperidine or a mixture of the two, to give tetraand pentacarbocyanines respectively. l' y Our new cyclammonium quaternary saltscontaining a reactive methyl group can be condensed with aldehydes, such as dialkylaminobenzaldehydes, dialkylaminocinnamaldehydes or the like to give dyes. The following examples'are illustrativenbut are not intended to limit our invention.

EXAMPLE 46.-1 (gn-dimethylaminostyryl) -benzothz'azo'le carbethoymethiodide 3.63 g. (l mol.) of l-methylbenzothiazole carbethoxymethiodide and 1.5 g. (1 mol.) of'p-dimethylaminobenzal-dehyde were heated together in 25 cc. of absolute ethyl alcohol containing four drops of piperidine catalyst at the reluxing temperature for about four hours.` The dye separated from the cooled reaction mixture. It was recrystallized from methyl alcohol and obtained as minute dark crystals having a blue reflex and giving a bluish-red methyl alcoholic solution. The dye melted at 218 to 220 C. with decomposition. It has the following formula:

EXAMPLE 47.-1(zi-diethylaminostyryl) -benzothz'azole p-ethoxyelthiodz'de ethoinretho-p-toluenesulfonate and 0.44 g. (1

, dark crystals having a steely reex and giving a bluish-red methyl alcoholic solution. It melted at 227 to 229 C. with decomposition and has the following formula:

above two examples the others of our new cyclammmonium quaternary salts containing a reactive methyl group can be condensed with dialkylaminobenzaldehydes and dialkylamlnocinnamaldehydes.

Our new dyes sensitize photographic emulsions in a novel and useful manner. `Our invention is particularly directed to the customarily employed silver halide emulsions especially the silver chloride and silver bromide emulsions, which may contain other salts which may be light sensitive. Our invention is further particularly directed to the customarily employed gelatin emulsions. However, the gelatin can be replaced with any other carrier which has substantially no deleterious effect on the light-sensitive materials, e. g. a

cellulose derivative or a resin.

In the preparation of photographic emulsions sensitized with our new dyes, it is only necessary to thoroughly disperse a, small amount of our dyes in an ordinary photographic emulsion. The suitable and most economical concentration for any given emulsion will be apparent to those skilled in the art upon making the ordinary tests and observations customarily employed in the art of emulsion making. To prepare a gelatino-silverhalide emulsion, the following procedure is satisfactory: A quantity of the dye is dissolved in a suitable solvent, for example methyl alcohol or acetone, advantageously the former, and a volume of this solution (which may be diluted with water if desired) containing from to 100 mg. of dye is slowly added to about 1000 cc. of an ordinary ilowable gelatino-silver-halide emulsion. The dye is thoroughly incorporated. With the more powerful of our new sensitizing dyes, to 20 mg. of dye per 1000 cc. of emulsion will suilce to produce maximum sensitizing effects with the ordinary gel-atino-silver-halide emulsions. In the case of our new tricarbocyanine dyes, about one mg. or less of dye per liter of emulsion is advantageously employed.A

The above statements are only illustrative and are not to be understood as limiting our invention in any sense as it will be apparent that these dyes can be incorporated by other methods in many of .the photographic emulsions customarily employed in the art, such for instance as by bathing a plate or nlm, upon which an emulsion has been coated, in a solution oi.' the dye in an appropriate solvent although such a method is ordinarily not to be preferred. The claims are intended to cover any combination of our new dyes with a photographic emulsion whereby the dyes exert a sensitizing effect upon the emulsion as well as a photographic element comprising a support. ordinarily transparent, upon which the light-sensi#` tive emulsion is coated or spread and permitted to set and dry.

The accompanying drawing is by way of illustration and is offered primarily to show the range of sensitivity of representative members of our longer chain dyes. Each figure of the drawing is a diagrammatic reproduction of a spectrogram showing the sensitivity o! an ordinary gelatino silver bromide emulsion containing one of our new dyes. In Fig. 1, the curve represents the emulsionA containing 2,2'.'li- (-carbethoxyethyl) thlacarbocyanine iodide. In Fig. 2, the curve represents the sensitivity of an ordinary gelatino silver bromide emulsion containing 2,2'di cyanoethyD-thiacarbocyanine iodide. In Fig. 3, the curve represents the sensitivity o! an ordinary` gelatine silver bromide emulsion containing 2,2'- di-(p-ethoxyethyl)-thiacarbocyanine iodide. In Fig. 4, the curve represents the sensitivity of an ordinary gelatino .silver bromide emulsion containing 1,1' -di- (-acetoxyethyl) -4,4' -carbocyanine iodide. In Fig. 5, the curve represents the sensitivity of an ordinary gelatine silver bromide emulsion containing 2,2'di (-acetoxyethyl) thlatricarbocyanine iodide.

Still further examples of our new emulsions could be given, but the foregoing will serve to teach those skilled in the art the principles of sensitizing emulsions with our new dyes. The illustrations have been confined to dyes of the longer chain types since it is this group of our dyes which is of the greatest utility in sensitizing emulsions.

In the specification and claims, by the term cyanine nitrogen atoms we mean the two nitrogen atoms essential to the cyanine dye chromo, phor, i. e. the two nitrogenatoms, the one tervalent and the other quinquevalent, which are linked together by a conjugated carbon chain. For example, in a dye such as 2,2'di(/Siethoxy4 ethyl) -rthiacarbocyanine iodide, which is formulated as follows:

there are two nitrogen atoms (the cyanine nitrogen atoms) 'linked together by a conjugated chain.

What we claim as our inve tion and desire to be secured by Letters Patent of the United States is:

1. A photographic gelatino-silver-halide emulsion sensitized with a sensitizing carbocyanine dye containing an alkyl group attached to each of the two nitrogen atoms, at least one of saidvcyanine dye containing anvalkyl group attached to each of the two nitrogen atoms, at least one of said alkyl groups being a -acetoxyethyl group.

5. A photographic gelatino-silver-halide emulcarbocyanine iodide.

6. A photographic gelatino-silver-halide emulsion sensitized with l,1di(acetoxyethyl) 4,4'

' carbocyanine iodide. sensitivity of an ordinary gelatine silver bromide I van alkyl group attached to each of the two cyanine nitrogen atoms, at least one of said alkyl groups being an alkyl group selected from the group consisting of alkoxyalkyl groups, acyloxyalkyl groups, carbalkoxyalkyl groups, -carboxy- .alkyl groups and acylalkyl groups which are devoid of Yaryl group substituents.

9. A photographic gelatinosilver-halide emulsion sensitized with a sensitizing cyanine dye containing an -alkyl group attached to each of the two cyanine nitrogen atoms, at least one of said .alkyl groups being an alkyl groupwselected from the group consisting of alkoxyalkyl groups, acyloxyalkyl groups, carbalkoxyalkyl groups, carboxylalkyl groups and acylalkyl groups which are devoid of aryl group substituents.

10. A photographic gelatino-silver-halide emulsion sensitized with a senstizing carbocyanine dye containing an alkyl group attached to each of the two cyaninenitrogen atoms, at least one of said alkyl groups being an alkyl group selected from the group consisting of alkoxyalkyl groups, acyloxyalkyl groups, carbalkoxyalkyl groups, carboxyalkyl groups and acylalkyl groups which are devoid of aryl group substituents.

11. A photographic gelatino-silver-halide emulsion sensitized with a sensitizing Vthiacarbocyanine dye containing an alkyl group attached to each of the two cyanine nitrogen atoms, at least one of said"alkyl groups being an alkyl group selected from the group consisting of alkoxyalkyl groups, acyloxyalkyl groups, Qarbalkoxyalkyl groups, carboxyalkyl groups and acylalkyl groups whichl are .devoidof aryl group substituents.

12.- A photographic gelatine-silver-halide emulsionr sensitized with a sensitizing- 4,4'rcarbocya ninedye containing an alkyl group attached to each of-.the two --cyanine nitrogen atoms, at least one of said alkyl. groups being an alkyl groupselected -rom -.the group consistingof alkoxyalkyl groups, acyloxyalkyl groups, carbalkoxyalkyl groups, carbpxyalkyl groups and acylalkyl groups which aref-devoid of aryl group substituents.

18..- =A photographic gelatino-silver-halide emulsion sensitized-'with a sensitizing tricarbocyanine dye containingn alkyl group attached to each of the` -twovcyanine nitrogen atoms, at least one of said alkyl groupsbeing an alkyl group selected 'from the group consisting of alko'xyalkyl groups, 

